1. Field of the Invention
The invention relates to an annular burner for an afterburner of a jet engine, for example for a reheat system of a bypass turbofan engine.
2. Summary of the Prior Art
Certain military multi-flow engines, equipped with a reheat system in the two flows, may comprise one or more annular burners serving strictly for postcombustion for heating of the secondary flow. Generally one of the afterburner rings is disposed at the conjunction of the two flows, just to the rear of the conical wall separating them.
The annular burner comprises an annular flame stabilizer of V-shaped cross-section containing a circular manifold for the injection of fuel discharging in counter flow through openings provided at the apex of the V cross-section.
As a result of the position of the annular stabilizer, its blades are subject to very different temperatures. The external blade is subjected to the flow of secondary air of which the temperature will not exceed 200.degree. C. whilst the internal blade is subject to a temperature of gases leaving the turbine, of the order of 850.degree. C.
Such differences in temperature give rise to varying high stresses and to strains in the annulus which are prejudicial to its successful operation and to its mechanical integrity.
French Patent Specification No. 2 186 608 proposes a solution to this reheat problem by disposing at a predetermined distance upstream of the annular burner an annular member termed an anvil, against which the jets emitted by the holes provided in the manifold are atomized. The mixture of gas and fuel produced and then atomized, passes through openings surrounding the jets and provided in the annular stabilizer, into the space surrounding the manifold in the annulus and protects the latter from the heat of the flame. Furthermore, the sheets of mist are uniformly charged with atomized fuel and dampen the external surface of the annular stabilizer which avoids hot spots and consequent excessive deformation.
The device described in this prior specification does not enable the avoidance of stresses in the annulus, which unfavourably influences the mechanical integrity. The principle aim of the anvil is the production of a uniform atomization of the fuel in the air flow and improved flame stability.